# How to calculate the spectral irradiance of an array of LEDs?

Good morning, how can I calculate this equation?

The LEDs have the following specifications:

https://www.mouser.com/datasheet/2/143/EAILP05RDDB1-708504.pdf

_ 12 LEDs; 3 second exposure; 20cm distance

Thank you very much for the help.

• What have you tried? – pericynthion Oct 19 '20 at 4:15
• There is enough information in that datasheet to make a rough estimate - spectral irradiance, wavelength graph, angle Vs magnitude. BUT measurement and comparison to datasheet max vale at say 0 degrees would be easier and probably more accurate. – Russell McMahon Oct 19 '20 at 6:27
• These are a PITA. 180 mW * efficacy / 0.5 sq.m (30deg @ 100mA @ 20 cm) = if an ideal LED = 0.00036 kW/m2. Vs. spec of 18 kW/m2 * 0.44... what U think? But centre is 2x as bright intensity 30 deg area edge but includes 95% of power used by Eir equation. – Tony Stewart EE75 Oct 19 '20 at 7:08
• then x 12 LEDs and ? efficacy gives result.. just don't try it at 5cm distance from eyeball. Opthmalogists use IR LED's to view the back of the eye briefly. – Tony Stewart EE75 Oct 19 '20 at 7:19
• just don't pretend to be an opthmalogist and view the back of the eye but OK for retina fiducial biometric scanning – Tony Stewart EE75 Oct 19 '20 at 7:22